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I've created a mandelbrot in php but the mandelbrot is looking a bit strange. How can I improve it? enter image description here

You can find a live example here: http://www.phpdevpad.de/index.php?id=190.

Update: Mandelbrot-Zoom with 900 iterations:

enter image description here

Update: I use this method of computing the mandelbrot:

double Re_factor = (MaxRe-MinRe)/(ImageWidth-1);
double Im_factor = (MaxIm-MinIm)/(ImageHeight-1);

double newMinRe = MinRe + (Re_factor* x1);
double newMaxRe = MinRe + (Re_factor* x2);
double newMinIm = MinIm + (Im_factor* y1);
double newMaxIm = MinIm + (Im_factor* y2);

// and then I compute c - real and c- imag values

  for(unsigned y=0; y<ImageHeight; ++y) 
{ 
  double c_im = newMinIm - y*Im_factor;
  for(unsigned x=0; x<ImageWidth; ++x)
    {
      double c_re = newMinRe + x*Re_factor;

      // ComputeMandelbrot();

     }

 }
  1. http://warp.povusers.org/Mandelbrot/
Micromega
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    Can you post a link to the source? Or include the relevant bits here? – ethrbunny Dec 02 '12 at 12:31
  • @ethrbunny: Done. Read my update. – Micromega Dec 04 '12 at 00:07
  • In the tutorial on Julia sets... A connected Julia set always contains the point 0+0i. A disconnected one does not contain that point. So by testing the point 0+0i for different values of K you can create a map of connected julia sets. This map IS the Mandelbrot set for that family of Julia sets. Mandelbrot discovered this shape quite literally by mapping julia sets. – phkahler Dec 04 '12 at 21:06

2 Answers2

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1) You need to increase the maximum number of iterations. The black areas are too large.

2) You can change the palate to something more interesting. The abrupt change to "blue" is weird.

3) The default picture of a woman should be larger and....

phkahler
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  • Try 300. Then try 1000. 60 is fine for a top level view, but as you zoom in more become necessary. Add iterations to a zoomed in picture to compare low and high number of iterations. – phkahler Dec 03 '12 at 21:58
  • For deep zoom, you may also need extended arithmetic precision. – lhf Dec 04 '12 at 00:12
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I'm guessing a few things are going on:

  1. As mentioned before, 60 iterations on a fractal like this will get you nowhere. Try 6000.
  2. You're likely running into the limits of precision of a double. That will eventually lead to blocky, and possibly incorrect renderings, especially as you zoom. You will need an exact number type. PHP does not offer a real exact data type natively, so you will have to either except minor inconsistencies related to the nature of floating point numbers or do some fun math yourself as integers or bytes.
mschultz
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  • LOL. It gives me max execution error with php. I need some better optimizations. It would be faster to write this is in JS? – Micromega Dec 04 '12 at 02:01
  • JS may be a better option - as the processing will take place on the client side, rather than on your server. – mschultz Dec 04 '12 at 02:03
  • In that case, it probably doesn't matter. It would appear that you have achieved your objective in rendering it in the first place, I would suggest looking into perhaps rendering a Julia set? – mschultz Dec 04 '12 at 02:07
  • Yes. Something like that. Or the optimizations from the wikipedia site (mandelbrot). I didn't understand it. – Micromega Dec 04 '12 at 02:08